Developers beware: Apple’s latest crackdown has started this weekend. App marketing companies have noticed that their apps that retrieve the end user’s Identifier for Advertisers (IDFA) but don’t show ads are getting rejected by the App Store, reports TechCrunch.

The move comes after Apple warned developers several times last year to make the necessary changes by rejecting apps using cookie-tracking and Mac-tracking methods. Now that the majority of developers have already started using it, Apple is informing them how to and how not to use IDFA.

The clause in particular which Apple is enforcing is 3.3.12:

“You and Your Applications (and any third party with whom you have contracted to serve advertising) may use the Advertising Identifier, and any information obtained through the use of the Advertising Identifier, only for the purpose of serving advertising. If a user resets the Advertising Identifier, then You agree not to combine, correlate, link or otherwise associate, either directly or indirectly, the prior Advertising Identifier and any derived information with the reset Advertising Identifier.”

It is worth mentioning here that ad networks charge advertisers based on installs. The advertiser sends the identifier toward the ad network for tracking purposes. By rejecting apps that doesn’t show ad functionality, Apple is sending a message to both advertisers and developers. The only problem is that the company’s reasoning is not entirely clear.

Some app marketing companies say Apple is after putting more control in the end user’s hands with the Advertising Identifier – and advertising identifier reset is equivalent to deleting cookies from your Web browser – while others say Apple is trying to put its iAd service in a better position.

Tapstream believes Apple is sending a signal to advertisers to switch to the Cost Per Click (CPC) method from Cost Per Install (CPI), which is the worst way for – advertisers. But the app marketing company also warns that the CPC method provides a poor user experience, so this move could be part of Apple’s fight against techniques used to move apps up in App Store’s charts through inorganic means, as even the usual app install ads can be used to manipulate the App Store’s top charts.